ZLDO330 查看數據表（PDF） - Diodes Incorporated.
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ZLDO330 Datasheet PDF : 9 Pages
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ZLDO330
APPLICATIONS
+5V In
IC1
ZLDO330
LBF Spg
SC Gnd
Vin D/C
N/C Vout
C3
100nF
+5V Out
C1
10pF
+3.3V Out
C2
1uF
0V In
Figure 1
0V Out
1). Simple 3.3V Supply
Using a circuit such as Figure 1, the ZLDO330
can easily provide a 3.3V logic supply from an
available 5V rail where most standard
regulators could not guarantee correct
operation. Although this approach is not
particularly energy efficient, if the load taken
at 3.3V is not too large, then the added
complexity and cost of a 3.3V switching
converter may not be justifiable and so this
linear solution can be preferable. This circuit
will also give far less noise than a switching
regulator which can be important when
handling low level analogue signals or low
voltage measurements.
Voltage
Feedback
D1
2). Post Converter Regulation
A common problem with multiple output
switch mode converters is that only one output
can be used in the feedback control loop of the
switching regulator. Thus only one output is
fully regulated. All other outputs are prone to
tracking errors that occur if the load on any
output changes significantly. By ensuring
close coupling of all transformer windings and
minimising the impedance of all outputs,
these errors can be reduced but never
eliminated. A simple way round this problem
is to wind the switching regulator transformer
to give a slightly higher voltage than required
and regulate down from this to the desired
voltage with a linear regulator. This is
indicated in Figure 2. To keep losses low and
so maintain the advantages of a switch mode
supply, it is important that the voltage drop
across this regulator is kept as low as possible,
i.e. just high enough to compensate for the
poor output impedance of the switching
power supply but no higher. The low dropout
voltage of the ZLDO330 allows this circuit
technique to be implemented very effectively,
giving a highly stable and accurate low noise
supply.
+ 5V Out
TR1
Switching
Regulator
C4
220uF
D2
ZLDO330
LBF Spg
SC Gnd
Vin D/C
N/C Vout
C1
10pF
+ 3.3V Out
Figure 2
C5
2 2 0 uF
4-67
C2
1uF
0V Out
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